Since photographic light-sensitive materials are generally composed of a support having an electrically insulating property and photographic layers, static charges often accumulate when the photographic light-sensitive materials are produced or used due to contact friction between the surfaces of the same or different kinds of materials or upon separation thereof from other materials. The accumulated static charges cause various difficulties. The most serious difficulty is that the light-sensitive emulsion layer is exposed to light due to discharge of the accumulated static charges prior to development. This causes dot spots or branch-like or feathery linear spots upon development of the photographic film. This phenomenon results in the so-called static marks, by which the commercial value of the photographic films is markedly decreased or, sometimes, completely destroyed. For example, it is easily understood that static marks result in a mistake in a judgment when they appear on medical or industrial X-ray films. Since this phenomenon only becomes evident upon development, it is a very troublesome problem. Further, the accumulated static charges cause secondary difficulties, for example, dust may adhere to the surface of the films or uniform application of photographic layers to the films cannot be achieved.
Such static charges often accumulate when photographic light-sensitive materials are produced or used, as described above. For example, during production, static charges arise due to contact friction between the photographic film and a roll or due to separation of the support surface and the emulsion surface when the photographic film is wound or rewound. Further, static charges are generated in an automatic photographing apparatus due to contact of the X-ray film with machine parts or with fluorescent sensitizing paper or upon separation therefrom. In addition, static charges are generated due to contact with packing materials, etc. Generation of static marks induced by accumulation of such static charges becomes rather substantial as the sensitivity of photographic light-sensitive materials is increased as the processing rate increases. Particularly, in recent years, static marks are more easily generated, because photographic light-sensitive materials have come to have high sensitivity and there are many opportunities for subjecting the materials to severe handling such as high speed application, high speed photography or high speed automatic processing, etc.
In order to aid in eliminating the problems created by static electricity, antistatic agents are preferably added to the photographic light-sensitive materials. Antistatic agents utilized in the photographic light-sensitive materials must have different characteristics than antistatic agents conventionally used in other fields because there are various restrictions which are characteristic to photographic light-sensitive materials. Antistatic agents which can be utilized in photographic light-sensitive materials must not only have excellent antistatic properties but they must not adversely influence the photographic properties, such as sensitivity, fog, granularity or sharpness. Further, they must not adversely influence the film strength of the photographic light-sensitive materials (namely, scratches are not easily formed by friction or scratching), they must not adversely influence antiadhesive properties (namely, the surface of the photographic light-sensitive material does not easily adhere to the surface of the photographic light-sensitive material or other materials), they must not promote fatigue of processing solutions for photographic light-sensitive materials, or they must not reduce the adhesive strength between layers of the photographic light-sensitive materials. Accordingly, the application of antistatic agents to photographic light-sensitive materials is restricted.
One method of removing difficulties due to static electricity comprises increasing the electrical conductivity of the surface of the photographic light-sensitive materials in order to disperse static charges in a short time before the accumulated charges are discharged.
Thus, methods of increasing the electrical conductivity of the support in photographic light-sensitive materials or various kinds of surface coating layers thereof have been proposed. Attempts have been made at utilizing various hygroscopic substances and water-soluble inorganic salts, certain kinds of surface active agents and polymers. For example, the use of polymers described in U.S. Pat. Nos. 2,882,157, 2,972,535, 3,062,785, 3,262,807, 3,514,291, 3,615,531, 3,753,716 and 3,938,999, etc., surface active agents described in U.S. Pat. Nos. 2,982,651, 3,428,456, 3,457,076, 3,454,625, 3,552,972 and 3,655,387, etc., and metal oxides and colloidal silica described in U.S. Pat. Nos. 3,062,700, 3,245,833 and 3,525,621, etc., is known.
However, it is very difficult to employ these substances in photographic light-sensitive materials because they are particularly suited for one kind of film support or photographic composition. Accordingly, they produce good results when used with a specified film support or photographic emulsion or other photographic elements. However, they are useless for preventing generation of static charges when used with different film supports and photographic elements, or they have an excellent antistatic properties but adversely influence the photographic properties such as sensitivity of the photographic emulsions, fog, granularity or sharpness, etc., or they have an excellent antistatic properties just after production but the antistatic properties deteriorate with the passage of time.
Nonionic surface active agents having one polyoxyethylene chain in the molecule are described in British Pat. No. 861,134 and German Pat. No. 1,422,309. These agents have excellent antistatic properties.
However, when they are employed in photographic light-sensitive materials the following problems occur: (1) sensitivity is markedly deteriorated, (2) since their antistatic properties deteriorate with the passage of time, although good antistatic properties just after production exist, the antistatic properties of products become inferior when the products are used, (3) when applied to X-ray-sensitive materials, dotted or meshlike uneven density (which is called "screen contamination") is formed on the X-ray-sensitive materials after development, because the sensitive materials come into contact with sensitizing paper (fluorescent screen) when photographs are made, and (4) the nonionic surface active agent in the light-sensitive material dissolves in the developer, contaminating the developer and rollers. This contamination sometimes attaches to the film that passes through the developer and rollers, slowing down the developing speed or soiling the film. These adverse effects aggravate the value of the product or sometimes lead to the total loss of the value of the product.
U.S. Pat. No. 3,850,641 discloses the use of an ethylene oxide adduct of a phenol-formaldehyde resin as an antistatic agent for photographic light-sensitive materials. This compound is somewhat superior to the above-mentioned nonionic surface active agent with only one polyoxyethylene chain per molecule thereof; however, it still is not completely free of the four disadvanrages described above.
Japanese Patent Application (OPI) Nos. 100546/80 and 74246/81 (the term "OPI" as used herein refers to a "published unexamined Japanese patent application") disclose the improvement of nonionic surface active agents through the introduction of a reactive group thereinto.
However, the sensitivity of photographic light-sensitive materials containing these nonionic surface active agents is greatly decreased and the intended performance is not exhibited.